1. Field of the Invention
This invention relates, in general, to pulse initiators for pulse operated metering systems and, more specifically, to opto-electronic pulse initiators which are responsive to the direction of rotation of the meter movement and which produce meter data pulses responsive to both the rate of meter movement and to the direction of meter movement.
2. Description of the Prior Art
Pulse initiators of the photoelectric or opto-electronic type are well known for use in electric utility metering systems. Such pulse initiators are typically associated with an integrating type meter, such as a watthour meter, to generate meter data pulses responsive to the rate of rotation of the watthour meter movement, which normally includes a rotating shaft and disc. Such opto-electronic pulse initiators are disclosed and claimed in U.S. Pat. No. 3,733,493, U.S. Pat. No. 3,878,391, and U.S. Pat. No. 3,943,498, all of which are assigned to the assignee of this invention. The opto-electronic pulse initiators described in these references are mounted to a meter and include a reflective pattern which is rotated by the meter movement. Basically, an optical sensing unit includes solid state radiation sensors for producing pulses as the reflecting surfaces of the pattern pass generally between the sensors and light emitting devices.
Although meters, such as watthour meters, are generally operated in one direction of meter movement, the pulse initiators described hereinabove respond to the rotational movement of the reflective pattern without respect to the direction of the movement of the pattern. Accordingly, the meter data pulses produced by occasional opposite directions of meter movement rotation are not distinguishable. Watthour meters are often provided with mechanical detent arrangements for preventing reverse rotation of the meter shaft and disc. This prevents reverse rotation of a pattern arrangement provided directly on the meter disc and prevents the dial registers of the meter from being operated in a down-scale direction. Other mechanical detent arrangements are also provided in other types of pulse initiators having a separate mechanism which is driven from the meter shaft by a gearing arrangement. The detent arrangements assure that the meter data pulses will be produced only in accordance with one direction of rotation of the pattern. The mechanical detents are also intended to prevent "creep" and small oscillating conditions occurring when the power consumption being measured by the meter is very low or zero.
Since many of the detent mechanisms include a ratchet wheel and pawl, some reverse rotation of the meter movement or gear train system can occur before locking engagement between the pawl and one of the ratchet teeth is accomplished. It has also been noted that in certain pulse initiator systems, the edges of the reflective surfaces may be positioned adjacent to the sensing unit in a stop or rest condition of the meter. Slight creeping or oscillating movement of the pattern relative to the sensing unit has also been noted to occur with the meter substantially stopped. Any one of these conditions can produce "false" pulses which erroneously indicate rotation of the meter movement.
In certain electric power metering systems, it is desirable to measure consumption of power which may flow in either of two directions. As one example, electrical energy can flow in opposite directions in a given set of conductors used for power exchange between electric utility companies. Pulse metering of bi-directional electrical energy can be provided by the prior art pulse initiators of the type disclosed hereinabove by using two meters which are equipped with pulse initiators that are arranged to operate only in opposite directions. Accordingly, one pulse initiator produces pulses indicating a measured electrical energy flow in one direction and the other pulse initiator produces pulses indicating the energy flow in the opposite direction. This is necessary since the pulse initiators are arranged to have only a single output and register power flowing in only one direction.
Therefore, it is desirable, and it is an object of this invention, to provide a pulse initiator system which is compatible with existing pulse initiator systems and which is capable of indicating the direction of power flow as well as the rate of power flow.